The present invention relates generally to an apparatus for the treatment of divided solid material and more particularly to a mixing apparatus for fluidizing and drying divided solid material in a vertical chamber.
In the processing of divided solid material, for example, the processing of foods such as flour, before packaging, it has been found to be desirable to create a fluidized bed of such material by feeding the material into a chamber and simultaneously feeding a pressurized gas such as air into the same chamber. For example, U.S. Pat. No. 3,075,298 to Schaub shows a cylindrical tower through which particulate material is fed in a downward direction from a screw feeder to a rotary valve output. Simultaneously, a treating gas under pressure enters the tower at the bottom thereof and passes upward through the falling particulate material at a rate insufficient to prevent the falling of the particulate material. This patented system also includes a plurality of guide members mounted on a centrally-located shaft within the tower. The shaft may be rotated during operation to thereby permit the guide members to force the falling particulate material into a helical flow pattern.
As an aid in controlling the exposure of the divided solid material to the gas, it has been proposed to place tubes lengthwise within the chamber so as to permit the divided solid material to pass downward through the tubes while simultaneously permitting the pressurized gas to pass upward through the tubes. This type of apparatus in the past has included a porous grid diffuser in the bottom portion thereof to disperse the incoming gas. However, this apparatus has tended to plug up, resulting in heat build-up within the chamber and frequent explosions.